Selenium cell



Feb, 26, 1929. l 1,703,798

H. THIRRING SELENIUM CELL Filed July 9, 1926 www PATENT OFFICE.

` HANS THIRBING, or VIENNA, AUSTRIA.

SELENIUM CELL.

Application led July 9, 1926, Serial No. 121,405, and in Austria July 20, 1925.

Selenium cells are known in which the system of supply electrodes consists of two sets of thin metal plates set on edge, each late of one s et entering between two. neigh ouring plates of the other set like comb teeth, the said metal plates being insulated from each other by mica plates. Such selenium cells are known as selenium cells of the condenser type. For making such a cell the face of the system of electrodes resembling a condenser formed by the edges is first ground and then Toughened by any suitable means for securing a good adhesion of the selenium afterwards applied thereto in the molten state.

For increasing the sensitivity and for reducing the lag in the action of the cells it is necessary to make the selenium coating as thin as possible. This causes difficulties in so far as the molten selenium tends to reduce its free surface when applied to a solid carrier and thereby to increase at the same time the thickness of the coating.

The ob'ect of the present invention is in the rst place to provide means whereby capillary action is utilized. These means consist, before all, in the use of a metal as the electrode material in relation to which selenium plays the part of a wetting liquid so that the molten selenium is drawn or soaked into the interstices between the metal and the insulating material. Such a metal is for instance pure copper, although any other metal which has the property of being wetted by molten selenium may be used. If molten selenium is applied to a carrier composed of alternating metal and mica plates set on edge, the metal employed being one capable of being wetted by liquid selenium, it will be observed on suitably heating a pile thus formed that a sort of sucking action is set up the layer of selenium ap lied to the carrier becoming progressively t inner.` Thus by properly selectmg the duration of the heating, any desired thickness may be imparted to the selenium layer.

For certain purposes selenium cells with a very small surface sensitive to li ht are required. In this case the carrier o the cell is rovided with a single pair of electrodes, the liitter being separatedv from each other by a layer of mica 0.1 to 0.2 millimeters in thickness. Now in this case it may happen that the sucking action of the two metal electrodes taken alone is too small to be able to properly reduce the thickness of the selenium layer' applied. This drawback may be remedied by providing on both sides of the surface sensitive to light between the supply electrodes proper and the frame of the cell additional metal plates insulated by mica. These additional metal plates do not carry current, but have only for their function to enable the surplus of selenium to be sucked in on sensibilizing the cell and thereby to reduce the thickness of the selenium layer.

Figure 1 is a plan view of one form of the invention,

Fig. 2 is an elevation of another form of the invention, Y

Fig. 3 is an elevation of Figure 1, as seen from the right, and

Fig. 4 is-a partial section on the line IV-IV of Fig. 3.

Fig. 1 showsa diagrammatical plan view of a cell constructed in accordance with the invention on a very large scale, such cell having a very small surface sensitive to light. 1 and l are the two electrodes, 2 are the insulating mica plates and 3 are the supply conductors. The selenium is indicated at 4. As this figure clearly shows each of the.two electrode'plates, 1 and 1' is not directly secured to the supply conductors 3 connected to the outside, but is repeatedly folded and passes toand fro in a closed zigzag, so that as the carrier for the selenium, a system of closely neighbouring metal strip? is formed, which, however, are separated y mica plates. Of course the selenium coating establishes connection only between the two electrodes. It need not, therefore, extend beyond the ends of the electrodes into the zigzag bent parts.

Fig. 2 shows by way of example a diagram matical section on a very large scale of another means having for its obJect to improve the adhesion of the selenium on its carrier. Here again 1 and 1 are the two electrode plates and 2 are the mica plates, and 4 is thev selenium. If the carrier is constructed in the manner heretofore yin use so that alternately one mica plate and one metal plate are located side by side, then the number of interstices between the plates is simply twice the number of electrodes. Now according to my invention the insulation between two successive electrodes is formed of a plurality of thin mica plates, as shown in Fig. 2, whereby the number of interstices in the selenium carrier is multiplied. This means has for its effect besides the reduction of the thickness of the layer, a firmer adhesion of the selenium to the carrier.

What I claim is:

1. In a selenium cell of the condenser type, metal plates consisting of av metal capable of being wetted by liquid selenium, in combination with insulating plates arranged between successive metal plates.

2. In a selenium cell of the condenser type, metal plates consisting of a metal capable of being wetted by liquid selenium, in combination with insulating plates arranged between successive metal plates, only two successive metal plates being electrodes, the selenium being soaked by capillary action between the metal and insulating plates to a comparatively great depth.

32 a selenium .cell of the condenser type, metal plates consistin of .a metal capable of being wetted by liqui selenium, in combination with insulating plates arranged between successive metal plates, only two successive metal plates being electrodes, the remaining nature. Y

HANS THIRRING. 

